There are several ways that drywall mastic (a.k.a., drywall mud) is applied over tape joints in the tape-and-bedding industry. Some simply use spatula blades to apply the drywall mastic, but this method requires great skill and training. Others use flat box devices, which are much faster to use, provide more consistent results, and usually better results than using a spatula blade. Flat box devices have been in use for many years now. Some of the more prevalent flat box devices are the “Ames style” or Ames brand flat boxes. These are often preferred by construction professionals.
FIGS. 1 and 2 show a 7-inch-wide Ames flat box device 20. FIG. 1 is a bottom perspective view of the flat box device 20. As illustrated in FIG. 1, most flat box devices have a mastic application opening 22 extending along a lateral direction (across most of the width of the device 20) on a bottom side 24 of the flat box device 20. This mastic application opening 22 is where the mastic exits the interior of the flat box device 20 and is evenly spread upon a surface during application. One of ordinary skill in the art in the tape-and-bedding industry will likely be familiar with the components and operation of the flat box device 20. The “Ames style” flat box device 20 shown in FIGS. 1 and 2 is representative of most flat box devices existing and in use in the industry today.
FIG. 2 is a front view of the flat box device 20 of FIG. 1 showing the front side 26 of the flat box device 20. As is typical with most flat box devices, the flat box device 20 of FIG. 2 includes a spring biased adjustment for the application blade 28 with adjustment screws 30 and pressure selection cam 32. For most Ames or “Ames style” flat box devices 20, the placement of the adjustment screws 30 (see FIG. 2) and the spacing of the adjustment screws 30 is about the same (for same size flat box devices). The relevance of this point will be more apparent later in the description section below.
A typical flat box device, like the flat box device 20 shown in FIGS. 1 and 2 for example, is adapted to apply mastic over tape joints along a flat surface. Such flat box devices can be used at or immediately adjacent to an outside corner or edge of a surface. But using a typical flat box device at an outside corner or edge requires great precision in handling the flat box device to obtain mastic cover all the to the edge or corner, and without leaving large lumps or deposits of unwanted mastic over the edge or on the other side of the corner. Maneuvering and handling the flat box device to avoid or minimize unwanted deposits over the edge requires more focus and slower movements, which makes the job slower and more difficult to master. Hence, there is a need for providing a way to allow a flat box device to be used at an outside corner or edge quickly, accurately, and easily, while still providing a high quality application of mastic with little or no unwanted mastic deposits over the edge or on the other side of the corner.
There have been several attempts in the prior art to resolve this problem by adding guide members to the flat box device. However, many of these solutions in the prior art required modification of existing flat box devices (drilling holes, permanently attaching brackets, etc.) or resulted in a flat box device dedicated to being used on outside corners or edges only. The problem with these solutions is that there are already existing many flat box devices that do not need to be replaced, which still have much life left for their use. Many workers do not want to bother with difficult modifications to the device requiring precise drilling and special tools to attach guides to existing flat box devices. Also, most workers do not desire to buy, nor carry around to job sites, multiple flat box devices. They would prefer few devices to buy and carry. Thus, a great need exists to utilize the existing flat box devices while providing a way to guide the flat box device along outside corners or edges. Also, most workers do not want to spend large sums of money to obtain a separate flat box device just for outside corners. Hence, there is a further need to inexpensively adapt and utilize existing flat box devices for applying mastic at outside corners and edges, quickly and accurately without preventing the existing flat box devices to still be used on flat surfaces (away from edges). This is also a need for a way to provide a guide device that is fast and easy to install without requiring special tools or machine work and without altering the original functionality of the flat box devices.